Protein Domain : Orange domain IPR003650

Type	Domain
Description	The Orange domain is a motif of ~35 amino acids present in eukaryotic DNA-binding transcription repressors, which regulate cell differentiation,embryonic patterning and other biological processes in both vertebrates and invertebrates. The Orange domain is located just C-terminal to a basichelix-loop-helix (bHLH) domain in the bHLH-Orange (bHLH-O) proteins. This family of bHLH repressors is related to the Drosophila hairy andEnhancer-of-split proteins, wherein the Orange domain was first described and also named helix III/IV region [, ]. The transcription of many vertebrate bHLH-O genes is regulated by the Notch signaling pathway, which controls fate decisions and other developmental processes. Orange domain proteins function as transcription repressors involved in the regulation of differentiation, anteroposterior segmentation and sex determination in flies [].Four subfamilies of bHLH-Orange proteins have been identified, i.e. hairy, Enhancer of split, Hey (also named HRT or Hesr) and Stra13 (also named SHARP,DEC, CLAST or BHLHB2) [ , ]. All these Orange domain proteins have the bHLH domain and except for the Stra13 subfamily, the othersubfamily members have a conserved tetrapeptide motif in the C-terminal extremity. The C-terminal motif of the hairy and Enhancer of split proteins isWRPW and this binds the transcriptional corepressor groucho/TLE. For the Hey subfamily members the C-terminal motif is YXXW. The Orange domain may conferspecificity of function to different family members and/or it may be involved in dimerization [, ].
Short Name	Orange_dom